[GlobalISel] Transform anyext(freeze(trunc(x))) to freeze(x) #165679
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We already have a transform for (anyext (trunc x)) -> x, this adds an extended version for (anyext (freeze (trunc x))) -> (freeze x). As we treat freeze i8 and i16 as legal this can help reduce the number of extends in the code.
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@llvm/pr-subscribers-llvm-globalisel Author: David Green (davemgreen) ChangesWe already have a transform for (anyext (trunc x)) -> x, this adds an extended version for (anyext (freeze (trunc x))) -> (freeze x). As we treat freeze i8 and i16 as legal this can help reduce the number of extends in the code. Full diff: https://github.com/llvm/llvm-project/pull/165679.diff 2 Files Affected:
diff --git a/llvm/include/llvm/Target/GlobalISel/Combine.td b/llvm/include/llvm/Target/GlobalISel/Combine.td
index 119695e53c3cb..a102e3f0c6a47 100644
--- a/llvm/include/llvm/Target/GlobalISel/Combine.td
+++ b/llvm/include/llvm/Target/GlobalISel/Combine.td
@@ -805,16 +805,28 @@ def redundant_sext_inreg: GICombineRule <
(defs root:$root),
(match (wip_match_opcode G_SEXT_INREG):$root,
[{ return Helper.matchRedundantSExtInReg(*${root}); }]),
- (apply [{ Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
+ (apply [{ Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
>;
-// Fold (anyext (trunc x)) -> x if the source type is same as
-// the destination type.
+// Fold (anyext (trunc x)) -> x if the source type is same as the destination
+// type.
def anyext_trunc_fold: GICombineRule <
- (defs root:$root, register_matchinfo:$matchinfo),
- (match (wip_match_opcode G_ANYEXT):$root,
- [{ return Helper.matchCombineAnyExtTrunc(*${root}, ${matchinfo}); }]),
- (apply [{ Helper.replaceSingleDefInstWithReg(*${root}, ${matchinfo}); }])
+ (defs root:$root),
+ (match (G_TRUNC $x, $src),
+ (G_ANYEXT $dst, $x):$root,
+ [{ return MRI.getType(${dst}.getReg()) == MRI.getType(${src}.getReg()); }]),
+ (apply (GIReplaceReg $dst, $src))
+>;
+
+// Fold (anyext (freeze (trunc x))) -> (freeze x) if the source type is same as
+// the destination type.
+def anyext_freeze_trunc_fold: GICombineRule <
+ (defs root:$root),
+ (match (G_TRUNC $x, $src),
+ (G_FREEZE $y, $x),
+ (G_ANYEXT $dst, $y):$root,
+ [{ return MRI.getType(${dst}.getReg()) == MRI.getType(${src}.getReg()); }]),
+ (apply (G_FREEZE $dst, $src))
>;
// Fold (zext (trunc x)) -> x if the source type is same as the destination type
@@ -2084,7 +2096,7 @@ def undef_combines : GICombineGroup<[undef_to_fp_zero, undef_to_int_zero,
def identity_combines : GICombineGroup<[select_same_val, right_identity_zero,
binop_same_val, binop_left_to_zero,
binop_right_to_zero, p2i_to_i2p,
- i2p_to_p2i, anyext_trunc_fold,
+ i2p_to_p2i, anyext_trunc_fold, anyext_freeze_trunc_fold,
fneg_fneg_fold, right_identity_one,
add_sub_reg, buildvector_identity_fold,
trunc_buildvector_fold,
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir b/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir
index 629238126380c..2b24a8920e0e0 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir
@@ -385,8 +385,8 @@ body: |
; CHECK: liveins: $h0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s16) = COPY $h0
- ; CHECK-NEXT: %2:_(s64) = nneg G_ZEXT [[COPY]](s16)
- ; CHECK-NEXT: $x0 = COPY %2(s64)
+ ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:_(s64) = nneg G_ZEXT [[COPY]](s16)
+ ; CHECK-NEXT: $x0 = COPY [[ZEXT]](s64)
%0:_(s16) = COPY $h0
%1:_(s32) = G_ANYEXT %0(s16)
%2:_(s64) = nneg G_ZEXT %1(s32)
@@ -401,10 +401,27 @@ body: |
; CHECK: liveins: $h0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s16) = COPY $h0
- ; CHECK-NEXT: %2:_(s64) = nneg G_ZEXT [[COPY]](s16)
- ; CHECK-NEXT: $x0 = COPY %2(s64)
+ ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:_(s64) = nneg G_ZEXT [[COPY]](s16)
+ ; CHECK-NEXT: $x0 = COPY [[ZEXT]](s64)
%0:_(s16) = COPY $h0
%1:_(s32) = nneg G_ZEXT %0(s16)
%2:_(s64) = G_ANYEXT %1(s32)
$x0 = COPY %2(s64)
...
+---
+name: test_combine_anyext_freeze_trunc
+body: |
+ bb.1:
+ liveins: $x0
+ ; CHECK-LABEL: name: test_combine_anyext_freeze_trunc
+ ; CHECK: liveins: $x0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+ ; CHECK-NEXT: [[FREEZE:%[0-9]+]]:_(s64) = G_FREEZE [[COPY]]
+ ; CHECK-NEXT: $x1 = COPY [[FREEZE]](s64)
+ %0:_(s64) = COPY $x0
+ %1:_(s32) = G_TRUNC %0(s64)
+ %2:_(s32) = G_FREEZE %1(s32)
+ %3:_(s64) = G_ANYEXT %2(s32)
+ $x1 = COPY %3(s64)
+...
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@llvm/pr-subscribers-backend-aarch64 Author: David Green (davemgreen) ChangesWe already have a transform for (anyext (trunc x)) -> x, this adds an extended version for (anyext (freeze (trunc x))) -> (freeze x). As we treat freeze i8 and i16 as legal this can help reduce the number of extends in the code. Full diff: https://github.com/llvm/llvm-project/pull/165679.diff 2 Files Affected:
diff --git a/llvm/include/llvm/Target/GlobalISel/Combine.td b/llvm/include/llvm/Target/GlobalISel/Combine.td
index 119695e53c3cb..a102e3f0c6a47 100644
--- a/llvm/include/llvm/Target/GlobalISel/Combine.td
+++ b/llvm/include/llvm/Target/GlobalISel/Combine.td
@@ -805,16 +805,28 @@ def redundant_sext_inreg: GICombineRule <
(defs root:$root),
(match (wip_match_opcode G_SEXT_INREG):$root,
[{ return Helper.matchRedundantSExtInReg(*${root}); }]),
- (apply [{ Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
+ (apply [{ Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
>;
-// Fold (anyext (trunc x)) -> x if the source type is same as
-// the destination type.
+// Fold (anyext (trunc x)) -> x if the source type is same as the destination
+// type.
def anyext_trunc_fold: GICombineRule <
- (defs root:$root, register_matchinfo:$matchinfo),
- (match (wip_match_opcode G_ANYEXT):$root,
- [{ return Helper.matchCombineAnyExtTrunc(*${root}, ${matchinfo}); }]),
- (apply [{ Helper.replaceSingleDefInstWithReg(*${root}, ${matchinfo}); }])
+ (defs root:$root),
+ (match (G_TRUNC $x, $src),
+ (G_ANYEXT $dst, $x):$root,
+ [{ return MRI.getType(${dst}.getReg()) == MRI.getType(${src}.getReg()); }]),
+ (apply (GIReplaceReg $dst, $src))
+>;
+
+// Fold (anyext (freeze (trunc x))) -> (freeze x) if the source type is same as
+// the destination type.
+def anyext_freeze_trunc_fold: GICombineRule <
+ (defs root:$root),
+ (match (G_TRUNC $x, $src),
+ (G_FREEZE $y, $x),
+ (G_ANYEXT $dst, $y):$root,
+ [{ return MRI.getType(${dst}.getReg()) == MRI.getType(${src}.getReg()); }]),
+ (apply (G_FREEZE $dst, $src))
>;
// Fold (zext (trunc x)) -> x if the source type is same as the destination type
@@ -2084,7 +2096,7 @@ def undef_combines : GICombineGroup<[undef_to_fp_zero, undef_to_int_zero,
def identity_combines : GICombineGroup<[select_same_val, right_identity_zero,
binop_same_val, binop_left_to_zero,
binop_right_to_zero, p2i_to_i2p,
- i2p_to_p2i, anyext_trunc_fold,
+ i2p_to_p2i, anyext_trunc_fold, anyext_freeze_trunc_fold,
fneg_fneg_fold, right_identity_one,
add_sub_reg, buildvector_identity_fold,
trunc_buildvector_fold,
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir b/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir
index 629238126380c..2b24a8920e0e0 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/combine-ext.mir
@@ -385,8 +385,8 @@ body: |
; CHECK: liveins: $h0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s16) = COPY $h0
- ; CHECK-NEXT: %2:_(s64) = nneg G_ZEXT [[COPY]](s16)
- ; CHECK-NEXT: $x0 = COPY %2(s64)
+ ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:_(s64) = nneg G_ZEXT [[COPY]](s16)
+ ; CHECK-NEXT: $x0 = COPY [[ZEXT]](s64)
%0:_(s16) = COPY $h0
%1:_(s32) = G_ANYEXT %0(s16)
%2:_(s64) = nneg G_ZEXT %1(s32)
@@ -401,10 +401,27 @@ body: |
; CHECK: liveins: $h0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s16) = COPY $h0
- ; CHECK-NEXT: %2:_(s64) = nneg G_ZEXT [[COPY]](s16)
- ; CHECK-NEXT: $x0 = COPY %2(s64)
+ ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:_(s64) = nneg G_ZEXT [[COPY]](s16)
+ ; CHECK-NEXT: $x0 = COPY [[ZEXT]](s64)
%0:_(s16) = COPY $h0
%1:_(s32) = nneg G_ZEXT %0(s16)
%2:_(s64) = G_ANYEXT %1(s32)
$x0 = COPY %2(s64)
...
+---
+name: test_combine_anyext_freeze_trunc
+body: |
+ bb.1:
+ liveins: $x0
+ ; CHECK-LABEL: name: test_combine_anyext_freeze_trunc
+ ; CHECK: liveins: $x0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+ ; CHECK-NEXT: [[FREEZE:%[0-9]+]]:_(s64) = G_FREEZE [[COPY]]
+ ; CHECK-NEXT: $x1 = COPY [[FREEZE]](s64)
+ %0:_(s64) = COPY $x0
+ %1:_(s32) = G_TRUNC %0(s64)
+ %2:_(s32) = G_FREEZE %1(s32)
+ %3:_(s64) = G_ANYEXT %2(s32)
+ $x1 = COPY %3(s64)
+...
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arsenm
reviewed
Oct 30, 2025
| %2:_(s32) = G_FREEZE %1(s32) | ||
| %3:_(s64) = G_ANYEXT %2(s32) | ||
| $x1 = COPY %3(s64) | ||
| ... |
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Can you add the negative test where the types mismatch? Also test multiple uses of the inner op
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We already have a transform for (anyext (trunc x)) -> x, this adds an extended version for (anyext (freeze (trunc x))) -> (freeze x). As we treat freeze i8 and i16 as legal this can help reduce the number of extends in the code.